The evolution of rifting on the volcanic margin of the Pelotas Basin and the contextualization of the Paraná–Etendeka LIP in the separation of Gondwana in the South Atlantic
The evolution of rifting on the volcanic margin of the Pelotas Basin and the contextualization of the Paraná–Etendeka LIP in the separation of Gondwana in the South Atlantic
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DOI：
10.1016/j.marpetgeo.2013.10.015
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发表时间：
2014-02
影响因子：
4.2
通讯作者：
Juliano Magalhães Stica;P. Zalán;André Luiz Ferrari
中科院分区：
文献类型：
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作者：
Juliano Magalhães Stica;P. Zalán;André Luiz Ferrari
佩洛塔斯盆地是火山被动边缘的典型例子，显示出向海倾斜的大楔形反射体（SDR）。 SDR 完全填充了整个盆地的裂谷，具有丰富的同裂谷岩浆作用（133-113Ma）。毗邻西部的巴拉那-埃滕德卡大型火成岩省 (LIP) 构成裂谷前岩浆作用 (134-132 Ma)。超深地震线的解释显示出与邻近的桑托斯盆地、坎波斯盆地和圣埃斯皮里图盆地截然不同的地质情况，这些盆地构成了贫岩浆被动边缘的例子。除了显示完全被火山岩填充的裂谷外，佩洛塔斯盆地还定义了不同的大陆地壳域，例如可能由高度拉伸和渗透的大陆火成地壳构成的外部域，以及可能反映底侵作用的高反射下地壳。南大西洋这部分裂谷的分析基于地震解释和区域线性磁异常的分布。 SDR 向东向未来裂解位置的横向增生及其裂谷和凹陷几何形状之间的时间关系允许重建盆地裂谷的演化。破裂从南向北分三个阶段（130–127.5；127.5–125；125–113 Ma）传播，物理上被海洋断裂带（FZ）分开。拉伸、减薄和严重侵入的大陆地壳宽度也呈现出同方向、同一自由区的三阶段增加。因此，大陆-海洋边界（COB）显示出从西到东、从南到北三个明显的转变，导致裂谷到边缘分割。在定义的三个部分中，裂谷也沿着最终分裂的方向从西向东传播。巴拉那-埃滕德卡 LIP 对西冈瓦纳大陆破裂和分裂的整个历史的重要性似乎在时间和空间上仅限于佩洛塔斯盆地。
The Pelotas Basin is the classical example of a volcanic passive margin displaying large wedges of seaward-dipping reflectors (SDR). The SDR fill entirely its rifts throughout the basin, characterizing the abundant syn-rift magmatism (133–113 Ma). The Paraná–Etendeka Large Igneous Province (LIP), adjacent to west, constituted the pre-rift magmatism (134–132 Ma). The interpretation of ultra-deep seismic lines showed a very different geology from the adjacent Santos, Campos and Espírito Santo Basins, which constitute examples of magma-poor passive margins. Besides displaying rifts totally filled by volcanic rocks, diverse continental crustal domains were defined in the Pelotas Basin, such as an outer domain, probably constituted by highly stretched and permeated continental igneous crust, and a highly reflective lower crust probably reflecting underplating.The analysis of rifting in this portion of the South Atlantic is based on seismic interpretation and on the distribution of regional linear magnetic anomalies. The lateral accretion of SDR to the east towards the future site of the breakup and the temporal relationship between their rift and sag geometries allows the reconstitution of the evolution of rifting in the basin. Breakup propagated from south to north in three stages (130–127.5; 127.5–125; 125–113 Ma) physically separated by oceanic fracture zones (FZ). The width of the stretched, thinned and heavily intruded continental crust also showed a three-stage increase in the same direction and at the same FZ. Consequently, the Continental-Oceanic Boundary (COB) shows three marked shifts, from west to east, from south to north, resulting into rift to margin segmentation. Rifting also propagated from west to east, in the direction of the final breakup, in each of the three segments defined. The importance of the Paraná–Etendeka LIP upon the overall history of rupturing and breakup of Western Gondwanaland seems to have been restricted in time and in space only to the Pelotas Basin.